This section provides background information related to the present disclosure which is not necessarily prior art.
The quality of semiconducting films deposited on various substrates is strongly dependent on the bonding and structural compatibility at the film-substrate interface. Differences in the crystalline symmetries or atomic periodicities between films being synthesized and supporting substrates generate strain and defects, resulting in poor quality of film growth. Some of these obstacles can be overcome by advantageously choosing substrate materials with certain atomic periodicities on their surface that can allow obtaining interfacial synergy between the films being synthesized and the substrate material, i.e., matching integer multiples of the interatomic spacing of the substrate with integer multiples of the film being grown on it. The most common approach for obtaining high-performance optoelectronic properties is based on film fabrication on lattice-matched, single-crystal substrates, which tend to be expensive, but can assure epitaxial growth with low defect densities. This is cost prohibitive for large area applications such as photovoltaic (PV) panels and light-emitting devices (LED) due to large substrate sizes and expenses. An alternate approach, which is applicable to a wide variety of substrate materials, crystalline and non-crystalline, including glass and plastics, is desired.
The absence of structural ordering at the interface of a thin film with amorphous substrate, promotes the growth of disordered or polycrystalline films. There is no known way to match a high-quality crystalline film to a substrate that has no underlying order. One way around this problem is the use of highly-textured metallic layers, such as Mo or Ti layers, on glass; this has been shown to improve optoelectronic material fabrication in PV cells and LED's, respectively. However, introducing highly-textured metallic layers on glass substrates results in more expensive and time intensive fabrication. A more cost effective and efficient fabrication process to form ordered high quality crystalline films would be desirable.